Frankfurt show: VW’s incredible diesel hybrid hero

LOOKING more like a Winter Olympics bobsleigh than a potential production car, the Volkswagen L1 presented in Frankfurt this week – which is billed as the most fuel-efficient automobile in the world – does in fact preview an all-new super-lean small eco model due for release in 2013.

The second generation of Volkswagen’s 2002 1-Litre car – claimed at the time to be the world’s first car with fuel consumption of 1L/100km, but destined to remain a development car due to its high-cost materials – the L1 two-seater diesel hybrid has emerged as a more viable model that “points the way toward the producton version”.

The European auto giant this week proclaimed: “The L1 represents a step forward into the future with completely new technology and a new design – revolutionary yet close to production readiness.” Tipping the scales at just 380kg, which is in large part due to its (124kg) carbon-fibre-reinforced plastic (CFRP) body, the L1 uses a newly developed 0.8-litre two-cylinder direct-injection common-rail turbo-diesel engine – derived from VW’s new 1.6 TDI unit – coupled with a 10kW electric motor and driving through a seven-speed DSG dual-clutch transmission.

According to Volkswagen, the combination of this rear-mounted drivetrain (which draws power from a front-mounted lithium-ion battery) represents the most fuel-efficient road-legal hybrid drive in the world – with the L1 rated with an incredible combined fuel consumption value of 1.38L/100km. CO2 emissions are also down to a new benchmark of 36g/km.

The hybrid system includes familiar technology such as engine idle-stop and regenerative braking but operates in two modes depending on load. In standard ‘Eco’ model, the 800cc TDI engine develops 20kW at 4000rpm, while in ‘Sport’ mode – which is needed to reach the car’s 160km/h top speed – power increases to 29kW (also at 4000rpm). Maximum torque is 100Nm at 1900rpm.

VW claims the 130-volt ‘E-motor’ provides a supporting role for the TDI engine in normal operations, but can provide 40 per cent additional torque over the entire engine speed range in conditions such as hard acceleration. It can also propel the L1 over short distances with pure electric power, with an auxiliary clutch automatically decoupling the TDI from the drivetrain as required.

Equipped with ABS brakes and ESP stability control, the L1 can reach 100km/h in a claimed 14.3 seconds. The fuel tank holds 10 litres, which VW claims is sufficient for a driving range of up to 670km, given the 1.38L/100km consumption.

The brilliant economy figure also stems from the L1’s small stature, wind-assisting design (with a drag coefficient of just 0.195Cd) and lightweight materials, such as a high aluminium content for the chassis, used in addition to the CFRP shell.

While the original 1-Litre car also used CFRP, which is considered the ideal material with its high strength and light weight, Volkswagen now claims to have succeeded in finding a production-viable and cost-effective way of producing CFRP parts in large enough volumes.

Energy-saving LEDs are used for front and rear lighting, while low-rolling-resistance 16-inch Michelin tyres are used front and rear – 95/60-section at the front, and 115/70 at the back (positioned behind removable wheel covers).

The underbody is completely enclosed for ultra-smooth airflow and the engine is cooled via “adapative air channels” integrated into the body sides. The latter automatically open and close based on the hybrid unit’s operating state and vehicle speed.

The L1 has a length of 3813mm, which is similar to that of the Volkswagen Fox light car sold overseas, while its 1143mm height, VW points out, is close to that of a Lamborghini Murcielago. The most asstonishing figure, though, is the 1200mm width – a narrowness VW claims no production car has ever managed.

Access to the cockpit is gained via a power-operated side-hinged roof cover. The tubular-frame CFRP seats are in bobsled formation, one behind the other, with the passenger seat part of the monocoque. The instrument panel has also been integrated into the monocoque and, likewise, is also made from CFRP. Other interior items are made from glass-fibre-reinforced plastic.

The L1 uses a start button which also serves as a gear selector switch (for drive, neutral, reverse and park) and is used to activate the electronic handbrake. The air-conditioning is adjusted via touch-sensors, while multi-functional keys on the steering wheel are used for the trip computer, satellite-navigation and stereo systems.

There are no wing mirrors or a conventional rear-view mirror, VW engineers substituting these for cameras displaying images on LED displays. A 50-litre storage compartment is located at the rear.

Overall, the interior furnishings weigh 35kg, the electrical system 20kg, the chassis 79kg and the drivetrain 122kg – which in turn leaves the aforementioned body weight of 124kg to achieve to the 380kg kerb weight.

“The design of the L1 redefines classic and aesthetic vehicle traits,” said VW design chief Walter de Silva. “Especially significant, of course, is how the nearly rocket-shaped lines catch one’s attention. All of its moving parts are integrated so accurately that the body resembles a rocket or jet.

“It is a body that cuts through the air with minimal aerodynamic resistance.” The L1 was presented in Frankfurt alongside the E-Up! light car, which is also due to hit the road in 2013, as well as the Golf R hot hatch, all-new Polo three-door, updated Transporter and Caravelle, and BlueMotion versions of the Polo, Golf and Passat.